porphyroblast

(from the article `metamorphic rock`) ...crystals showing planar surfaces—namely, magnetite, garnet, epidote, mica, calcite, quartz, and feldspar. Minerals that have a tendency to form ...
Found on http://www.britannica.com/eb/a-z/p/95

porphyroblast

A large crystal of a mineral such as garnet or staurolite set in a matrix of much finer-grained minerals in a metamorphic rock. compare phenocryst.
Found on http://www.ge-at.iastate.edu/glossary-of-geologic-terms/
No exact match found